The Gemara on 35a brings the Mishnah of Malveh al HaMashkon (a case of a Shomer Sachar, where there's seemingly no Shvua She Aino B'Rshuso) as a Kasha against Rav Huna, who says Shomrim who pay must swear Aino B'Rshuso. This is surprising, because the Mishnah in Shavuos was a case of a Shomer with a Tainas Chiyuv (i.e. Shomer Sachar who claimed the Mashkon was "Ne'evad"); NOT a case of a Shomer with a Tainas Ptur who chooses to pay. Who said Rav Huna holds Shomrim who make a Tainas Chiyuv and have to pay must take a Shvua She Aino B'RShuso? Rav Huna spoke in reference to the Mishnah on 33b, a case of Shomer Chinam who claimed "Nigneveh", a Tainas Ptur for him; perhaps it is only in that situation that he holds a Shomer must swear Aino B'RShuso?
A few possible Tirutzim:
A- It is a Kol She'Kain. If a Shomer must swear Aino B'Rshuso when he makes a Tainas Ptur and pays (low level of suspicion), for sure he must swear Aino B'Rshuso when he makes a Tainas Chiyuv and pays (high level of suspicion). The Sma in C.M. Siman 295 says this very Svara and explains: it raises more red flags when you claim a Tainas Ptur and choose to pay (instead of swearing to Patur yourself) than when you admit the truth that you are Chayiv and pay.
(This Svara seemingly runs contrary to the Svara of the Ritva, quoted in the Shita, who says that from Rav Sheshes on B.M. 6a, we would only know you need to swear Aino B'RShuso when you make a Tainas Ptur and actually swear to Patur yourself; that's where we're Choshesh that the Shomer may want to keep the Pikadon for himself. The Chiddush of Rav Huna is that even when you choose to pay instead of swearing to Patur yourself, we're still Choshesh and you still need to swear Aino B'RShuso. However, it could be that the Ritva was only contrasting the level of suspicion by a Shomer who makes a Tainas Ptur and swears to Patur himself (high) vs a making a Tainas Ptur and paying (low). He might agree with the Sma that a Shomer who makes a Tainas Ptur and pays, while less suspicious than a Shomer who makes a Tainas Ptur and swears, is still more suspicious than a Shomer who makes a Tainas Chiyuv and pays.)
B- Indeed, Rav Huna spoke in reference to the Mishnah on 33b, a case of Shomer Chinam who claimed "Nigneveh", but that doesn't necessarily indicate a Tainas Ptur. The Rivan, for e.g. holds that the case of the Mishnah is "Nigneveh B'Pshiah", i.e. a case of Tainas Chiyuv. If so, the Gemara's Kasha on Rav Huna from the Mishnah of Malveh al HaMashkon, a case of a Shomer Sachar who made a Tainas Chiyuv and is paying, is quite parallel.
C- According to the Rif (according to the understanding of the Rosh and the Bach), Rav Huna spoke not in reference to the Mishnah (a case of Shomer Chinam who claimed a Tainas Ptur of "Nigneveh" and chooses to pay instead of swearing), but in reference to the Din of R'Yochanan (that a Shomer who says "Hareini Mishalem" instead of swearing gets the Keifel even before he pays). The Gemara extends the Din of R'Yochanan to even include Shomerim who claim a Tainus Chiyuv and choose to pay (instead of swearing falsely). Thus, when Rav Huna said "We administer him a Shvua She Aino B'Rshuso" he was referring to all Shomerim who say "Hareini Mishalem", whether they make a Tainas Ptur or a Tainas Chiyuv. According to the Rif, then, the Gemara's Kasha on Rav Huna from the Mishnah of Malveh al HaMashkon, a case of a Shomer Sachar who made a Tainas Chiyuv and is paying, is also parallel.
Daniel Steinberg, Columbus
1)
a) The Sefer Me'iras Einayim (S'ma) OC 395:3 does not write that it is a "Kol she'Ken." The S'ma writes that if it he makes a Ta'anas Petur there is a high level of suspicion (not a low level). Since, according to his argument, he is exempt from paying, why would he want to pay if not for the fact that he has taken a liking to the object and wants to keep it for himself? The Chidush is that even if he makes a Ta'anas Chiyuv, when he admits that he is Chayav, one might have thought that he is telling the truth, and even so we are worried that he might have taken a liking to the object and is saying this only in order to keep it.
b) The Shitah Mekubetzes (34b, DH v'Zeh Lashon ha'Ritva) in the name of the Ritva is identical to the S'ma in what he writes that even when he pays -- and we might have thought that we do not suspect him of taking a liking to the object -- we are suspicious (because we say that people think that one is allowed to take other people's property without their agreement if they pay the full price).
c) The Ritva writes that this is the very Chidush of Rav Huna, that even for a Ta'anas Petur he must swear. If we do not say that Rav Huna maintains that one must swear even for a Ta'anas Petur, we cannot understand what Rav Huna has added to the Din of Rav Sheshes (Rami bar Chama) above on 6a.
(The Ritva has the Girsa of "Rami bar Chama" on 6a, unlike our Girsa of "Rav Sheshes.")
d) The S'ma writes that a Shomer who makes a Ta'anas Petur and pays is more suspicious than a Shomer who makes a Ta'anas Chiyuv and pays.
2) The Rivan (in Tosfos 33b, DH Nignevu) is like the S'ma who writes that even though the Shomer Chinam said he was Poshe'a, he still must swear.
3) At first sight, it seems to me that to explain what the Chidush of Rav Huna is according to the way the Rosh learns in the Rif, one is also going to need the explanation of the S'ma. I will have to think more about this, bs'd.
4) I looked again at the Rif and I must confess that I am confused. As you wrote, Reb Daniel, the Rosh 3:1 writes in the name of the Rif that Rav Huna is referring to the Din of Rebbi Yochanan. The Rosh writes in the Shitah of the Rif that as long as he has not sworn or paid he does not rely on him, but he says that he has taken a liking to the object. This implies that if he has paid, then we no longer are worried that he has taken a fancy to the object. This is not like the S'ma 295:3 who writes that even if a Shomer Chinam admits he was Poshe'a (and therefore must pay) we still are afraid that he has taken a liking to the object, as I wrote above. It is also not like the Shitah Mekubetzes (34b, DH v'Zeh Lashon ha'Ritva) that even if he pays we are worried that he has taken a liking to the object (again as I wrote above). So it seems that the Rif is a new Shitah -- that if he paid we no longer are worried "Shema Einav Nasan Bo." We are going now to get back the question of the Ritva: what is Rav Huna adding more than Rav Sheshes (Rami bar Chama) above on 6a?
I think we are at the beginning of a big Sugya.
5) I looked more into the Shitah of the Rif and, firstly, it should be pointed out that there is a big difference between the way the Rosh learns the Rif and the way the Bach learns the Rif. According to the Rosh, it does not make a difference whether he said "Hareini Meshalem" or whether he actually did pay; he always must take a Shevu'ah that it is not in his Reshus. According to the Bach, if the Shomer paid, this means that by accepting the payment the Mafkid was Mochel to the Shomer so the Shomer does not need to take a Shevu'ah.
I want to suggest that according to the Bach we can answer the question of the Ritva, that what did Rav Huna on 34b tell us new that we did not already know from 6a? The answer is that this in itself is the Chidush of Rav Huna -- that we are Medayek from him that it is only if he said "Hareini Meshalem" that he must swear, but if he paid, this creates a Petur from the Shevu'ah.
Kol Tuv,
Dovid Bloom